Try this Gaynor.
First click Notifications, Inbox, then scroll down to My Settings, My Account and click General Settings. Then scroll down to Thread Display Options and uncheck "Show Signatures". Then shut down your internet browser (IE?).
Restart the browser, go into edit signature again and remove the offending part, check preview and then click Save Signature.
Now go back into General Settings as above and recheck "Show Signature". Close and reopen your browser and see if that has done the trick on one of your posts.